The answer, clearly, is "so cute." And so loved, from the looks of it. Spears, 30 -- already a doting mom to sons Sean Preston, 7, and Jayden James, 6, her children with ex-husband Kevin Federline -- has been showing off the newest addition to her family all over town.

On Nov. 19, the singer and her family -- minus fiancé Jason Trawick -- took their puppy shopping at Petco to buy pet supplies. A source tells Us the star also had Hannah in tow on the "X Factor" set last week.

By Monday morning, Brit's dog was so famous that it had its own Twitter account, with messages like "Woof!" and "Should I wear a bow? Mom says I'm a princess & that I need a bow."